2021-04-16 : Activated abilities contain a colon and appear in the form “[Cost]: [Effect].” Some keywords (such as equip) are activated abilities and will have colons in their reminder texts. Loyalty abilities of planeswalkers are also activated abilities.

2021-04-16 : An activated ability that costs mana to activate is not a “mana ability” unless it could also produce mana and has no targets.

2021-04-16 : Casting Revel in Silence in response to a spell or ability won’t affect that spell or ability. That is, it’s not countermagic.